Thermal Stability Of Bulk Metallic Glasses Research Articles

Glass formation in Fe-Cr-Zr-B-Mo alloys by tuning Nb addition

Fe-based bulk metallic glasses (BMGs) with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal. The high glass forming ability (GFA) and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying. In order to meet these requirements, the influence of Nb content on the GFA of Fe57Cr10Zr8B18Mo7−xNbx (x=1–5, at.%) alloys was investigated, as Nb has positive roles in GFA and thermal stability of BMGs. The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe57Cr10Zr8B18Mo5Nb2 and Fe57Cr10Zr8B18Mo4Nb3 alloys. The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K, respectively. The mechanism for improving their GFA was analyzed based on the principle of metal solidification, the parameters for glass formation and thermal properties of the alloys. The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV, 2,062 MPa and 1,180 HV, respectively. The developed BMGs with high B content, good GFA, and very high hardness can be used as coating materials to the framework for spent nuclear fuels.

Effects of heat treatment on the thermal, mechanical and corrosion properties of deformed Zr-based bulk metallic glasses

The effects of heat treatment at different temperatures in the supercooled liquid region on the thermal properties, mechanical properties and corrosion behaviors of deformed Zr65Cu15Ni12.5Al7.5 bulk metallic glasses (BMGs) are studied. Scanning electron microscope (SEM), differential scanning calorimetry (DSC), potentiodynamic polarization and electrochemical impedance are performed to characterize surface morphology, thermal properties, and corrosion resistance. Furthermore, the uniaxial compression test is conducted to investigative the mechanical properties of the alloy. The thermal stability of BMGs is apparently reduced as the heat-treated temperature increases. The as-cast possesses a maximum plastic deformation of about 19.5%. However, with the increase of heat-treated temperature, the plastic strain of the samples decreases, which is about 14.5% (at 643 K for 10 min), 9.5% (at 663 K for 10 min), and 3.0% (at 683 K for 10 min), respectively. Additionally, the corrosion resistance of the deformed alloys after heat treatment is superior to that of the deformed alloys before heat treatment, but it is still not as good as that of the as-cast.

Effect of Sn on Glass Formation Ability and Crystallization Behaviors of Cu-Based Bulk Metallic Glass Alloy

Cu-based bulk metallic glasses (BMGs) with 5 mm in diameter were synthesized by copper mold casting. The effects of tin (Sn) addition on glass-forming ability (GFA), thermal stability of BMGs were investigated. It was found the addition of 4 at. % Sn is effective for an increase in GFA. The crystallization behaviors of Cu-based bulk metallic glasses during continuous heating are investigated mainly by differential scanning calorimeter(DSC).The results show that the characteristic temperatures(Tg,Tx and Tp) shifted to high temperature region with increasing of heating rates. The activation energies Eg, Ex and Ep, corresponding to characteristic temperatures Tg, Tx, and Tp, respectively, were obtained from Kissinger and Ozawa equations. The calculated activation energies agree well with Kissinger or Ozawa equations due to the almost invariability of the crystallization volume fraction at the characteristic temperatures for different heating rates.

Role of minor alloying additions in formation of bulk metallic glasses: A Review

Minor alloying addition or microalloying technology has already shown dramatic effects on glass formation and thermal stability of bulk metallic glasses (BMGs). This paper intends to provide a comprehensive review of recent developments of this technology in the field of BMGs. The beneficial effects of minor alloying additions on the glass formation and the thermal stability of BMGs will be summarized and analyzed. In addition, principles and guidelines for future application of this technology will also be proposed.